title: Immunological evaluation of a synthetic Clostridium difficile oligosaccharide conjugate vaccine candidate and identification of a minimal epitope.
abstract: Clostridium difficile is the cause of emerging nosocomial infections that result in abundant morbidity and mortality worldwide. Thus, the development of a vaccine to kill the bacteria to prevent this disease is highly desirable. Several recently identified bacterial surface glycans, such as PS-I and PS-II, are promising vaccine candidates to preclude C. difficile infection. To circumvent difficulties with the generation of natural PS-I due to its low expression levels in bacterial cultures, improved chemical synthesis protocols for the pentasaccharide repeating unit of PS-I and oligosaccharide substructures were utilized to produce large quantities of well-defined PS-I related glycans. The analysis of stool and serum samples obtained from C. difficile patients using glycan microarrays of synthetic oligosaccharide epitopes revealed humoral immune responses to the PS-I related glycan epitopes. Two different vaccine candidates were evaluated in the mouse model. A synthetic PS-I repeating unit CRM197 conjugate was immunogenic in mice and induced immunoglobulin class switching as well as affinity maturation. Microarray screening employing PS-I repeating unit substructures revealed the disaccharide Rha-(1→3)-Glc as a minimal epitope. A CRM197-Rha-(1→3)-Glc disaccharide conjugate was able to elicit antibodies recognizing the C. difficile PS-I pentasaccharide. We herein demonstrate that glycan microarrays exposing defined oligosaccharide epitopes help to determine the minimal immunogenic epitopes of complex oligosaccharide antigens. The synthetic PS-I pentasaccharide repeating unit as well as the Rha-(1→3)-Glc disaccharide are promising novel vaccine candidates against C. difficile that are currently in preclinical evaluation.
authors.affiliation: Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
authors.forename: Christopher E
authors.initials: CE
authors.lastname: Martin
authors.forename: Felix
authors.initials: F
authors.lastname: Broecker
authors.forename: Matthias A
authors.initials: MA
authors.lastname: Oberli
authors.forename: Julia
authors.initials: J
authors.lastname: Komor
authors.forename: Jochen
authors.initials: J
authors.lastname: Mattner
authors.forename: Chakkumkal
authors.initials: C
authors.lastname: Anish
authors.forename: Peter H
authors.initials: PH
authors.lastname: Seeberger
mesh_terms: D001428:Bacterial Vaccines / Q000737:chemistry / Q000276:immunology*; D002236:Carbohydrate Conformation; D016360:Clostridioides difficile / Q000737:chemistry* / Q000276:immunology; D004761:Enterocolitis, Pseudomembranous / Q000276:immunology / Q000628:therapy*; D000939:Epitopes / Q000276:immunology*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000737:chemistry / Q000276:immunology*; D014614:Vaccines, Synthetic / Q000737:chemistry / Q000276:immunology*
chemical_list: D001428:Bacterial Vaccines; D000939:Epitopes; D009844:Oligosaccharides; D014614:Vaccines, Synthetic